I. Field of the Invention
The present invention relates to a device for constituting in the wall of a pipe an optical pick-up window which may be scavenged by a current of protective fluid.
The invention is particularly applied to the protection of the active surface of a pick-up serving to determine the degree of pollution of a fluid.
For example, it is a question of a detector for detecting hydrocarbon in water rejected into the sea, or of a pick-up for the detection of pollutant impurities in fumes.
II. Description of the Prior Art
Hydrocarbons such as gas oils, fuel oils and lubricating oils present in the bilge water in ships are separated before being rejected into the sea. The separation is not complete and a maximum threshold is fixed by the legislation in force. It is therefore necessary to monitor the water rejected. This control is made by measuring the light diffused by the micro-droplets of hydrocarbon illuminated by a beam of light.
It happens that the measurement is falsified in the long run by the deposit of hydrocarbons on the window and it has already been proposed to eliminate or substantially decelerate the formation of hydrocarbon deposit on the window by a suitable scavenging of the window by means of a fluid which is sent onto the window and then into the pipe.
In practice, eddies are frequently produced in front of the window when the scavenging fluid passes in the pipe and it is an object of the present invention to provide a device which does not produce eddies which may falsify the measurements.